2 Repair welding is a favorable choice rather than replacement parts. This is because it
is more economical, faster and reliable approach to bring a part back to service when failure of the part is encountered. The failure of the weld may be due to the incorrect
processes or poor workmanship, for example incomplete weld penetration in the early of fabrication stages. Besides that, there is also a possibility where
inappropriate selection of filler metal that used for welding operation. Another cause that leads to failure of weld is deterioration during service, where the working
environment is corrosive or accentuated by stress corrosion Cary, 2002.
1.2 Problem Statement
Dissimilar metal welding has gained its popularity and well-established in catering the requirement of transition in mechanical properties andor variation of service
environments Lippold and Kotecki, 2005. This method is especially popular in pharmaceutical industry, in which the fabrication of pressure vessel involved joining
of two different types of stainless steel material. Most of the time austenitic type is the primary choice for pharmaceutical equipment due to their remarkable properties,
particularly corrosion resistance and weldability. For instance, vessels made from AISI 304 and AISI 316L are joined together but they work in different circumstances,
where vessels AISI 316L have contact with working media, yet AISI 304 does not SK Group, 2012.
Since pharmaceutical equipment always subjected to high temperature and pressure, they are more susceptible to premature failure after a certain service period and it
becomes more critical when there is involvement of dissimilar metal weld joints. This is because dissimilar metal weld joints have higher tendency encountered to
material degradation such as thermal aging. Besides that, dissimilar metal weld joint has other problems such as carbon migration from high alloy to low alloy side or
formation of brittle intermetallic compound Mvola et al., 2014. In addition, any cracking or other stress concentrators found in the weld joint also greatly affected the
structural integrity of the part. Consequently, the lifespan of the part is shortened and it can bring severe disaster due to the unexpected failure Kyung et al., 2012.
3 As a result, repair welding is often desired in industry to prolong the service lives or
enhance performance of the components by providing remedy for presence of welding defects during initial stages or weld deterioration during their service
Zeinoddini et al., 2013. Besides that, it is more economical to perform repair welding rather than purchase a new component as the purchasing cost is certainly
higher. Moreover, repair welding is comparatively cost-effective than make replacement of the part. This is because delay time during waiting the replaced part
might cause an irreparable lost to a company Total Materia, 2004. Moreover, repair welding is undeniably useful in giving indication for usability and safety of a
component or part Gupte, n.d.. Overall, repair welding is important in saving cost, minimizing break down time and extending service life of a part American Welding
Society, 2014.
Nevertheless, limited research has been done on the repair welding that involved dissimilar metals. Majority of the researcher are focused on the repair welding of
single metal type. Therefore, the effect of repair welding on AISI 304 and AISI 316L will be emphasized in this study. Based on the changes of mechanical properties and
microstructural transformation after each weld repair, the useful service life of this dissimilar metal joint can be anticipated.
1.3 Objectives
